Method, computer program control and regulating unit for operating an internal combustion engine, as well as an internal combustion engine

ABSTRACT

In an internal combustion engine, the fuel is conveyed by an electrically driven fuel pump. The intake side of this pump is connected to a fuel tank and its outlet side is connected to a pressure region. A prerun of the electrically driven fuel pump may be performed before the startup of the internal combustion engine. In order to increase the service life of the fuel pump, an actual pressure (pactual) in the pressure region may be detected by a pressure sensor and the execution of the prerun be a function of at least the signal of the pressure sensor.

FIELD OF THE INVENTION

The present invention relates to a method of operating an internalcombustion engine, in which the fuel is conveyed by an electricallydriven fuel pump, whose intake side is connected to a fuel tank andwhose outlet side is connected to a pressure region, and in which aprerun of the electrically driven fuel pump may be performed before theinternal combustion engine is started, an actual pressure in thepressure region being detected by a pressure sensor and the execution ofthe prerun being a function of at least the signal of the pressuresensor.

BACKGROUND INFORMATION

In a conventional method, the fuel is conveyed from a fuel tank into apressure region by an electrical fuel pump. A fuel injector is connectedto this region. This injector is in turn positioned in an intakemanifold of the internal combustion engine. In this manner, the fuel mayreach the intake manifold via the fuel injector and from there reach thecombustion chambers of the internal combustion engine. A further methodof the type initially cited is known from internal combustion engineswhich operate using gasoline direct injection. In these internalcombustion engines, the fuel is conveyed by an electrical fuel pump,which is also referred to as a “presupply pump,” from the fuel tank intoa pressure region, and from there reaches a high-pressure fuel pump(“main supply pump”), which is generally mechanically driven. This pumpconveys the fuel further into a common fuel line (“rail”). Multipleinjectors are connected to this rail, and the fuel is stored at highpressure therein. The injectors each inject the fuel directly into thecorresponding combustion chambers of the internal combustion engine.

If the electrical fuel pump and the pressure region positioneddownstream from it are configured as a “constant-pressure system,” thepressure region is connected via a mechanical pressure regulator to thefuel tank. In normal operation, the electrically driven fuel pumpconveys the fuel continuously and at the maximum output rate. In theknown internal combustion engines and/or the known methods, any quantityof fuel which is not sprayed into the intake manifold by the fuelinjector in systems having intake manifold injection, and which is notconveyed further by the high-pressure pump in systems having gasolinedirect injection, flows back into the fuel tank via the mechanicalpressure regulator.

Since the electrically driven fuel pump runs continuously at the maximumoutput rate, it is ensured that the pressure in the pressure regionalways remains at the desired level, even if the maximum possiblequantity of fuel is demanded by the fuel injector and/or the injectors.

Demand-controlled fuel systems are also known. These are alsoconstant-pressure systems, in which the pressure in the pressure regionis set to a constant value through the activation of a mechanicalpressure regulator. The fuel pump is therefore no longer activatedfully, i.e., continuously at maximum output, but rather only accordingto the demand of the internal combustion engine. The excess quantity offuel flows back into the tank via a mechanical pressure regulator. Theadjustment of the conveyance output to the instantaneous operating pointof the internal combustion engine causes a savings in fuel, since thedrive output of the electrically driven fuel pump may be reduced in manyoperating ranges of the internal combustion engine.

During startup of the internal combustion engine, sufficient pressuremust be provided in the pressure region of the fuel system so that thefuel reaches the combustion chambers of the internal combustion enginein the desired manner. Typically, it is assumed that the pressure of thefuel in the pressure region falls to ambient pressure after the internalcombustion engine is shut off. In order to be able to achieve a desiredpressure for starting the internal combustion engine, at least thequantity of fuel necessary for compressing the fuel to the desiredpressure must therefore be conveyed. The expansion of the fuel systemduring the pressure buildup must also be taken into consideration. Insome known methods, the operating time of the fuel pump, which is drivenat constant output, during the prerun is a function of the period oftime which has passed since the internal combustion engine was shut off.

Using the shutoff time of the engine, a fuel system pressure, the numberof pump preruns which have already occurred, etc., for example, ascriteria for requiring a fuel pump prerun is described in GermanPublished Patent Application No. 199 61 298.

German Published Patent Application No. 100 14 550 describes thepossibility of controlling the fuel pressure during the prerun on thebasis of a pressure sensor by changing the speed of the fuel pump.

In this method, the conveyance output of the electrically driven fuelpump during the prerun is tailored to the particular demand. This demandis defined by the signal provided by the pressure sensor. If thepressure sensor signals that the pressure in the pressure region islower than desired, the electrical fuel pump is activated accordingly.In contrast, if the pressure sensor signals that the pressure in thepressure region already corresponds to the desired pressure, theelectrical fuel pump remains switched off.

SUMMARY

It is an object of the present invention to provide a method such thatthe internal combustion engine may start even more reliably and, at thesame time, the prerun of the electrically driven fuel pump may be asshort as possible.

This object may be achieved in a method such that the electrical fuelpump is initially operated at maximum output during a prerun.

An example embodiment of the method according to the present inventionmay provide that it may be ensured that the pressure of the fuel in thepressure region necessary for an optimum start of the internalcombustion engine is reached as rapidly as possible during the prerun,and the electrical fuel pump may only be activated for the shortestpossible time. This may facilitate and accelerate starting the internalcombustion engine, since the fuel pressure necessary for this purpose isreached very rapidly.

In an example embodiment, the execution of the prerun may be a functionof whether a prerun has already been performed in the current operatingcycle. In this manner, a prerun of the electrical fuel pump may beprevented from being executed after a vehicle in which the internalcombustion engine is installed is briefly switched off and started. Thisalso may avoid the electrical fuel pump from being put into operationunnecessarily.

Furthermore, a prerun of the electrical fuel pump may be executed if theactual pressure is at least equal to a specific value or lower than aspecific value and/or the prerun may be ended if the actual pressurereaches or exceeds a specific value. This procedure may also shorten theoperating time of the electrical fuel pump.

Alternatively or additionally, it is possible for the prerun of theelectrical fuel pump to be ended if the duration of the prerun reachesor exceeds a specific value. This may prevent the electrical fuel pumpfrom running too long if it is impossible to build up pressure in thefuel system (therefore, this provides a type of “safety cutoff”). In theevent of cold external temperatures, the batteries which supply theelectrical fuel pump may also be prevented from being overloaded by anexcessively long prerun of the electrical fuel pump.

A possibility of reaching the maximum output during the prerun of theelectrical fuel pump which is easy to implement is for the output of thefuel pump to be influenced by a PI regulator as a function of thedifference between the detected pressure and a setpoint pressure in thepressure region, and by a precontroller as a function of the setpointpressure, and for the integrator of the PI regulator to be initializedas follows for a prerun of the electrical fuel pump: maximum possibleactivation output minus normal precontrol output minus activation outputof the P component of the PI regulator.

As an alternative, it is possible for the output of the fuel pump to beinfluenced by a PI regulator as a function of the difference between thedetected pressure and a setpoint pressure in the pressure region and bya precontroller as a function of the setpoint pressure and, for a prerunof the electrical fuel pump in the precontroller, for an additionalprerun precontrol output to be added to the normal precontrol output insuch a manner that the overall precontrol output is initially at amaximum. This may be implemented using software and may ensure that thepressure in the pressure region is built up at maximum rate. However,this method may simultaneously prevent an overshoot occurring after theend of the prerun of the electrical fuel pump. This is a concern if theintegrator of the PI regulator is initialized using a relatively highvalue. Because the activation of the electrical fuel pump at maximumoutput is caused by the precontroller in this case, an initialization ofthis type is not necessary.

In a refinement to this procedure, the additional precontrol output maybe produced by giving the value zero to the input of a low-pass filterat the beginning of the prerun of the electrical fuel pump and thelow-pass filter may be initialized using the following value: maximumpossible activation output minus normal precontrol output. In this case,as above, the normal precontrol output is understood as the precontroloutput which results from the instantaneous setpoint pressure in thepressure region of the fuel system. Such a method may be implementedusing software. Through the low-pass filter, the electrical fuel pump isinitially operated at maximum output. The additional precontrol outputis therefore initially at maximum (it corresponds to the difference ofmaximum possible activation output and normal precontrol output) andthen falls to zero following an exponential function.

In this case, the time constant of the low-pass filter may be a functionof the difference between the actual pressure and the setpoint pressurein the pressure region. In this case, the setpoint pressure may be avalue which is not subjected to a limitation of the maximum gradients,as is typical. If the difference between actual pressure and setpointpressure is very large, the additional precontrol output decaysrelatively slowly to zero. If the difference is small, the decay occursmore rapidly.

Furthermore, the setpoint pressure in the pressure region may be afunction of the temperature in a region of the internal combustionengine, at least for the prerun of the electrical fuel pump. If theinternal combustion engine is warm, possibly existing vapor bubbles maybe compressed by an elevated pressure in the pressure region. If theinternal combustion engine is cold, in contrast, the prerun time may beshortened with this example embodiment.

The present invention also relates to a computer program which issuitable for performing the method above when it is executed on acomputer. In this case, the computer program may be stored in a memory,e.g., in a flash memory, a ferrite RAM, etc.

Furthermore, the present invention relates to a control and/orregulating unit for operating an internal combustion engine in which thefuel is conveyed by an electrically driven fuel pump, whose intake sideis connected to a fuel tank and whose outlet side is connected to apressure region. In order to improve the start quality of the internalcombustion engine and to reduce the exhaust gas emissions duringstarting, the control and/or regulating unit may include a memory inwhich a computer program of the type above is stored.

Furthermore, the present invention relates to an internal combustionengine including a fuel system, which includes a fuel tank, anelectrically driven fuel pump, whose intake side is connected to thefuel tank and whose outlet side is connected to a pressure region, aprerun of the electrically driven fuel pump being executable beforestarting the internal combustion engine, and a pressure sensor beingprovided which detects an actual pressure in the pressure region, andthe execution of the prerun being a function of at least the actualpressure. In order to improve the start quality of the internalcombustion engine and to reduce the exhaust gas emissions duringstarting, the internal combustion engine may include a control and/orregulating unit of the type above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an internal combustion engineincluding an electrical fuel pump.

FIG. 2 is a flow chart which illustrates a method of executing a prerunof the electrical fuel pump from FIG. 1.

FIG. 3 is a flow chart which illustrates a method of determining theactivation output of the electrical fuel pump for the prerun in FIG. 2,the method including a precontroller and a PI regulator.

FIG. 4 is a flow chart which illustrates a first possibility fordetermining the activation output of the electrical fuel pump for theprerun in detailed form.

FIG. 5 is a flow chart similar to FIG. 4, which illustrates anotherpossibility for determining the activation output of the electrical fuelpump for the prerun.

DETAILED DESCRIPTION

In FIG. 1, an internal combustion engine is indicated as a whole byreference number 10. It includes multiple combustion chambers, only oneof which is illustrated in FIG. 1, using reference number 12. Combustionchamber 12 may be connected to an intake manifold 16 via an intake valve14. A fuel injection device 18 is positioned in intake manifold 16. Athrottle valve 20 and an air mass meter 22, implemented as a hot filmsensor (“HFM sensor”) are also located upstream from fuel injectiondevice 18 in the intake manifold. Combustion chamber 12 may be connectedto an exhaust gas pipe 26 via an outlet valve 24. A fuel-air mixture incombustion chamber 12 may be ignited by a spark plug 28. This spark plugis activated by an ignition system 30.

Fuel injection device 18 is part of a fuel system 32. This systemincludes a fuel tank 34, from which an electrically driven fuel pump 36conveys the fuel into a fuel line 38, which leads to fuel injectiondevice 18. Fuel line 38 is connected to an overflow valve 40 downstreamfrom electrically driven fuel pump 36. A line (without reference number)leads from this valve to an ejector pump 42, which is arranged in theregion of fuel tank 34.

The fuel pressure existing in fuel line 38 is detected by a pressuresensor 44. This sensor supplies appropriate signals to a control andregulating unit 46, which also receives signals from HFM sensor 22 and aspeed sensor 48, which picks up the speed of a crankshaft 50 of internalcombustion engine 10. Furthermore, signals from a temperature sensor 52,which detects the temperature of an engine block of internal combustionengine 10, are supplied to control and regulating unit 46. A positionsensor 54, which detects the position of an ignition key 56, is alsoconnected to control and regulating unit 46. Electrically driven fuelpump 36, overflow valve 40, ejector pump 42, and pressure sensor 44 maybe implemented as one module in fuel tank 34.

On the output side, control and regulating unit 46 activates, amongother things, ignition system 30, throttle valve 20, and fuel injectiondevice 18. Furthermore, the activation output of electrical fuel pump 36is also set by control and regulating unit 46. This is performed byactivating a clock module 58, which outputs a pulse duty factor. Theactivation output of electrically driven fuel pump 36 is thus varied viapulse width modulation (PWM).

For starting internal combustion engine 10 (i.e., as soon as theignition is switched on), the procedure is as follows, as illustrated inFIG. 2: after a starting block 60, it is queried in a block 62 whether aprerun of electrical fuel pump 36 has already occurred in the currentoperating cycle and whether an actual pressure pactual detected bypressure sensor 44 is lower than a limit value G1. The start in block 60is initiated when a specific position of ignition key 56 is detected byposition sensor 54. The query as to whether a prerun of electrical fuelpump 36 has already occurred in the current operating cycle is performedby checking a bit B1. This check provides the result “false” if a prerunof electrical fuel pump 36 has already occurred in the current operatingcycle.

If one of the two conditions or both conditions are not fulfilled inblock 62, no prerun is executed. In contrast, if both conditions arefulfilled, clock module 58 is activated in block 64 and electrical fuelpump 36 is put into operation. The activation output, whereby electricalfuel pump 36 is activated, is calculated according to a method which isdescribed in greater detail below in connection with FIGS. 3 to 5.

In block 66, bit B1 is set, indicating that a prerun of electrical fuelpump 36 was executed in the current operating cycle. As long as a prerunof the electrical fuel pump is being executed, a bit B2 is set. In block68, it is queried whether actual pressure pactual of the fuel in fuelline 38 is greater than or equal to a limit value G2. In the presentcase, both limit values are identical. However, limit values G1 and G2may also be different. In addition, it is queried in block 68 whetherperiod tekp, which corresponds to the operating time of electrical fuelpump 36 during the prerun, is greater than or equal to a limit value G3.When one of the two conditions is fulfilled, the prerun of electricalfuel pump 36 is ended in block 70. In order to save calculating time,the conditions for a prerun of the electrical fuel pump are no longercalculated when the internal combustion engine is in normal operation.This is also determined by querying an appropriate bit.

In the internal combustion engine illustrated in FIG. 1, the activationoutput of electrical fuel pump 36 is determined as a function of, amongother things, actual pressure pactual and a setpoint pressure pset in acombination including a PI regulator and a precontroller. The setpointvalue for the pressure in fuel line 38 is primarily a function of thecurrent operating parameters of internal combustion engine 10, e.g., ofthe temperature of internal combustion engine 10 detected by temperaturesensor 52, the speed of crankshaft 50 detected by speed sensor 58, theair charge detected by HFM sensor 22, and the position of ignition key56 detected by position sensor 54. The pressure in fuel line 38 is setby an appropriate variation of the voltage (and consequently the speedand/or the torque) of fuel pump 36. The determination of the activationoutput of electrical fuel pump 36 is illustrated in a more general formin FIG. 3:

Subsequently, actual pressure pactual in fuel line 38 is detected inblock 74. The corresponding signal is provided by pressure sensor 44. Inactual pressure detector 74, the voltage signal provided by pressuresensor 44 is averaged over ten measurement values and this averagevoltage value is converted into a raw pressure value via apressure-voltage characteristic curve of pressure sensor 44. The rawpressure value is filtered in a block 76, from which actual pressurepactual results, and this pressure value pactual is supplied to a PIregulator (block 78).

The signals of HFM sensor 22, speed sensor 48, temperature sensor 52(and possibly, for example, also position sensor 54 of ignition key 56or signals resulting therefrom) are used in a block 80 to calculate asetpoint pressure pset. This pressure is also supplied to PI regulator78. In accordance with the difference between setpoint pressure pset andactual pressure pactual, a regulator output rgl is determined in PIregulator 64, in normal operation of internal combustion engine 10. Thisoutput is produced in the form of a specific pulse duty factor, as istypical for pulse width modulation. Setpoint pressure pset and thesignals of sensors 22, 48, 52, and 54 are also used, however, in block82 for generating a precontrol output vsl.

The determination of the precontrol output for a prerun of electricalfuel pump 36 may occur in various manners. The goal is to provide adesired pressure in fuel line 38 as rapidly as possible. For thispurpose, electrical fuel pump 36 is to be activated using maximum outputat least at the beginning of the prerun. A possibility for providingthis maximum activation output at the beginning of the prerun isillustrated in FIG. 4. In this case, the special requirements of theprerun of electrical fuel pump 36 are taken into consideration inprecontroller 82. Firstly, however, the determination of normalregulator output rgl and normal precontrol output vsl for the normaldynamic operation of electrical fuel pump 36 (i.e., when internalcombustion engine 10 is running) will be described with reference toFIG. 4:

A regulator output rgl for the dynamic operation of electrical fuel pump36 is determined as follows: in PI regulator 78, difference dp betweensetpoint pressure pset and actual pressure pactual is formed in 84. Thisdifference dp is fed into a proportional regulator 86 and an integrator88. Proportional regulator 86 provides a proportional component dpp, andintegrator 88 provides an integral component dpi. Both components dppand dpi are added in 90 and converted into regulator output rgl in block92. In order to prevent overload of integrator 88, integral componentdpi is delimited by limit values max and min, which are provided inmemories 94 and 96.

Precontrol output vsldyn for dynamic operation is determined as follows:a fuel volumetric flow vol1 is determined from speed nmot, which isprovided by speed sensor 48, a motor constant C1, which is stored in amemory 98, and relative fuel mass rk, which is provided in block 100 bymultiplication in 100. This fuel volumetric flow is the volumetric flowwhich reaches combustion chamber 12 through fuel injection device 18during operation of internal combustion engine 10.

A second component vol2 is added to this fuel volumetric flow vol1 in102. This volumetric flow is established in turn from a characteristiccurve 104, which is addressed using setpoint pressure pset. Fuelvolumetric flow vol2 is the volumetric flow which flows from fuel line38 via overflow valve 40 (which may also be implemented as a pressurerelief valve) to ejector pump 42 and/or back into fuel tank 34. The sumof both components vol1 and vol2 provides the overall fuel volumetricflow vol to be conveyed by electrical fuel pump 36. This sum is fed,together with setpoint pressure pset, into a characteristic map 106,which outputs precontrol output vsldyn for dynamic operation ofelectrical fuel pump 36.

Now regarding the determination of activation output asl during a prerunof electrical fuel pump 36: in order to be able to initially activateelectrical fuel pump 36 at maximum output during a prerun of this pump,the difference between maximum permissible activation output aslmax ofelectrical fuel pump 36 and precontrol output vsldyn for dynamicoperation is formed in precontroller 82 if a prerun is to be executed.Maximum permissible activation output aslmax is stored in a memory 110and is a function, for example, of clock module 58 used, which generatesa pulse duty factor (the output pulse duty factor is a function of theinput pulse duty factor).

A low-pass filter 112 is initialized using the difference formed in 108.A time constant T of low-pass filter 112 is determined in 114 using acharacteristic curve, into which difference dp between actual pressurepactual and setpoint pressure pset is fed. Setpoint pressure pset isfree in this case of a gradient delimitation, while in contrast it isgradient-delimited for the determination of fuel volumetric flow vol2and for the use in regulator 78. The value zero is given to the input oflow-pass filter 112. The output of low-pass filter 112 provides aprecontrol output vslvor for the prerun of electrical fuel pump 36. In116 this output is added to precontrol output vsldyn for the dynamicoperation of internal combustion engine 10 and results in totalprecontrol output vsl. In 118, this output is added in turn to regulatoroutput rgl and provides overall activation output asl.

Activation output asl for a prerun of electrical fuel pump 36 isdetermined as follows: since internal combustion engine 10 is not yet inoperation during the prerun of electrical fuel pump 36 and thereforecrankshaft 50 does not yet rotate, the multiplication in 100 results inthe value zero. Precontrol output vsldyn for the dynamic operation ofinternal combustion engine 10 thus results exclusively from fuelvolumetric flow vol2 and setpoint pressure pset. In the prerun ofelectrical fuel pump 36, setpoint pressure pset results from acharacteristic map as a function of speed nmot and a load rl or, as inthe present case, from the temperature of internal combustion engine 10,which is provided by temperature sensor 52.

However, precontrol output vsldyn determined in 106 for the dynamicoperation of internal combustion engine 10 is relatively low. Acondition signals that a prerun is to occur and enables low-pass filter112. The condition is that if a time tnse is less than a limit valuegtvt, low-pass filter 112 is enabled. Due to the initialization oflow-pass filter 112 using the difference between precontrol outputvsldyn and maximum permissible activation output aslmax, precontroloutput vslvor for the prerun of electrical fuel pump 36 initiallycorresponds exactly to this difference. Since this difference is addedin 116 to precontrol output vsldyn for the dynamic operation, precontroloutput vsl at the beginning of the prerun of electrical fuel pump 36corresponds to maximum permissible activation output aslmax ofelectrical fuel pump 36. Electrical fuel pump 36 thus initially rotatesat maximum speed and maximum output, so that the pressure in fuel line38 is built up at maximum speed. As was explained above, time constant Tof low-pass filter 112 is formed as a function of the difference betweensetpoint pressure pset and actual pressure pactual. A large differenceresults in a comparatively large time constant T, while a smalldifference results in a correspondingly small time constant T. Thismeans that with a large difference between pset and pactual, precontroloutput vsl decays slower from the initialization value to zero than witha small difference. Since in this manner the difference between actualpressure pactual and setpoint pressure pset is to become smallerrelatively rapidly during the prerun of electrical fuel pump 36, a largeintegral component dpi does not built up in integrator 88 of PIregulator 78, so that an overshoot due to the regulator is avoided whenactual pressure pactual reaches setpoint pressure pset. In addition, anoverflow of the integrator is prevented in that the integrator isstopped by an appropriate bit when the maximum pulse duty factor isoutput, but actual pressure pactual is simultaneously less than setpointpressure pset.

A second possibility, using which activation output asl of electricalfuel pump 36 may be established during a prerun of electrical fuel pump36, is illustrated in FIG. 5. Those functions which may ensure thatelectrical fuel pump 36 is activated at maximum output at the beginningof the prerun are implemented in FIG. 5 not in precontroller 82, butrather in PI regulator 78. It is to be noted at this point that thoseelements, blocks, and functions which may be functionally similar toelements, blocks, and functions of FIG. 4 have identical referencenumbers and are not explained again in detail in each case.

Similarly to FIG. 4, a precontrol output vsldyn for the dynamicoperation of internal combustion engine 10 is determined in block 82.Also similarly to FIG. 4, the difference between maximum permissibleactivation output aslmax of electrical fuel pump 36 and precontroloutput vsldyn for the dynamic operation of internal combustion engine 10is formed in 108. This difference is converted in 120 into a pressurevalue, from which proportional component dpp, which was established inproportional regulator 86, is subtracted in 122. Integrator 88 isinitialized using the value resulting therefrom.

As a result, at the beginning of a prerun of electrical fuel pump 36,regulator output rgl, resulting from the sum of proportional componentdpp and integral component dpi in 90, i.e., 92, is equal to thedifference between maximum permissible activation output aslmax ofelectrical fuel pump 36 and precontrol output vsldyn for the dynamicoperation of internal combustion engine 10. Since regulator output rglis added in 118 to precontrol output vsldyn, an activation output aslwhich is equal to maximum permissible activation output aslmax resultsat the beginning of the prerun of electrical fuel pump 36. As thedifference between actual pressure pactual and setpoint pressure psetbecomes smaller, the regulator output then falls again, so that totalactivation output asl is also reduced.

It is to be noted that the initialization of integrator 88 asillustrated in FIG. 5 and the determination of precontrol output vslvoras illustrated in FIG. 4 is performed each time the condition “ignitionon” is detected (initialization of the engine control unit). Therefore,both steps are performed during a prerun of electrical fuel pump 36 andduring a normal start of internal combustion engine 10 without a prerun.It is also to be noted that the concept of “output” used in connectionwith FIGS. 3 through 5 may also be expressed in practice by a voltagevalue, a current value, or a pulse duty ratio.

1. A method of operating an internal combustion engine, comprising:delivering a fuel by an electrically driven fuel pump that includes anintake side connected to a fuel tank and an outlet side connected to apressure region; detecting an actual pressure in the pressure region bythe pressure sensor; and executing a prerun of the electrically drivenfuel pump before startup of the internal combustion engine as a functionof at least a signal of the pressure sensor, the prerun includingoperating the electrical fuel pump initially at maximum output andthereafter at an output level dependent on the signal provided by thepressure sensor.
 2. The method of claim 1, wherein the prerun isexecuted as a function of whether the prerun has already been executedin a current operating cycle.
 3. The method of claim 1, furthercomprising at least one of the steps of: executing the prerun of theelectrical fuel pump if the actual pressure is one of at least equal toa first specific value and lower than the first specific value; andterminating the prerun of the electrical fuel pump when the actualpressure one of reaches and exceeds a second specific value.
 4. Themethod of claim 1, further comprising the step of: terminating theprerun of the electrical fuel pump if a duration of the prerun one ofreaches and exceeds a specific value.
 5. A method of operating aninternal combustion engine, comprising: delivering a fuel by anelectrically driven fuel pump that includes an intake side connected toa fuel tank and an outlet side connected to a pressure region; detectingan actual pressure in the pressure region by the pressure sensor;executing a prerun of the electrically driven fuel pump before startupof the internal combustion engine as a function of at least a signal ofthe pressure sensor, the prerun including operating the electrical fuelpump initially at maximum output; influencing an output of the fuel pumpby a PI regulator as a function of a difference between the actualpressure and a setpoint pressure in the pressure region and by aprecontroller as a function of the setpoint pressure; and initializingfor the prerun of the electrical fuel pump, an integrator of the PIregulator in accordance with a one of a value of a maximum possibleactivation output minus a normal precontrol output minus an activationoutput of a P component of the PI regulator and a value corresponding tothe value of the maximum possible activation output minus the normalprecontrol output minus the activation output of the P component of thePI regulator.
 6. A method of operating an internal combustion engine,comprising: delivering a fuel by an electrically driven fuel pump thatincludes an intake side connected to a fuel tank and an outlet sideconnected to a pressure region; detecting an actual pressure in thepressure region by the pressure sensor; executing a prerun of theelectrically driven fuel pump before startup of the internal combustionengine as a function of at least a signal of the pressure sensor, theprerun including operating the electrical fuel pump initially at maximumoutput; influencing an output of the fuel pump by a PI regulator as afunction of a difference between the actual pressure and a setpointpressure in the pressure region and by a precontroller as a function ofthe setpoint pressure; and adding, for the prerun of the electrical fuelpump, an additional prerun precontrol output to a normal precontroloutput in the precontroller so that an overall precontrol output isinitially at a maximum.
 7. The method of claim 6, wherein the additionalprecontrol output is produced in that, at the beginning of the prerun ofthe electrical fuel pump, a value zero is given to an input of alow-pass filter and the low-pass filter is initialized using one of afirst value of a maximum possible activation output minus a normalprecontrol output and a second value corresponding to the first value.8. The method of claim 7, wherein a time constant of the low-pass filteris a function of a difference between the actual pressure and thesetpoint pressure in the pressure region.
 9. The method of claim 1,wherein a setpoint pressure in the pressure region is a function of atemperature in a region of the internal combustion engine, at least forthe prerun of the electrical fuel pump.
 10. A computer program on atangible computer-readable medium configured to be executed by acomputer, the computer program comprising program code for operating aninternal combustion engine in accordance with a method including:delivering a fuel by an electrically driven fuel pump that includes anintake side connected to a fuel tank and an outlet side connected to apressure region; detecting an actual pressure in the pressure region bythe pressure sensor; and executing a prerun of the electrically drivenfuel pump before startup of the internal combustion engine as a functionof at least a signal of the pressure sensor, the prerun includingoperating the electrical fuel pump initially at maximum output andthereafter at an output level dependent on the signal provided by thepressure sensor.
 11. The computer program of claim 10, wherein thecomputer program is stored in a memory.
 12. The computer program ofclaim 11, wherein the memory includes at least one of a flash memory anda ferrite RAM.
 13. A control device for operating an internal combustionengine of a motor vehicle, the comprising: a memory configured forstorage of a computer program including program code for operating theinternal combustion engine in accordance with a method including:delivering a fuel by an electrically driven fuel pump that includes anintake side connected to a fuel tank and an outlet side connected to apressure region; detecting an actual pressure in the pressure region bythe pressure sensor; and executing a prerun of the electrically drivenfuel pump before startup of the internal combustion engine as a functionof at least a signal of the pressure sensor, the prerun includingoperating the electrical fuel pump initially at maximum output andthereafter at an output level dependent on the signal provided by thepressure sensor.